This invention relates to a sound processing system for processing a sound waveform received from a sound source.
A conventional sound processing system processes an input sound waveform employing, for example, a digital signal processor. FIG. 7 illustrates a typical digital signal processor 141 which includes a multiplier 141a, an adder 141b, and two buffers 141c and 141d. The digital signal processor 141 processes a received digital signal and outputs the digital signal processed in a desired manner. The process of the digital signal processor 141 proceeds rapidly utilizing a pipelining process, in which the execution of a command and the fetch of the next command occur synchronously and generally simultaneously.
An example of such a digital signal processor employed for processing sound waveforms is illustrated in FIG. 8 wherein it is generally indicated as 151. The digital signal processor 151 includes a memory 157a, a multiplier 153, an offset circuit 155, and a memory 157d. The offset circuit 155 is provided with multipliers 159, 161, 163, 165 and 167, and adders 169, 171 and 173, The exemplary offset circuit 155 thus executes an offset process for an input sound waveform, establishing the multiplication coefficients of the six multipliers 153, 159, 161, 163, 165 and 167 appropriately.
FIG. 9 shows an example of the offset process performed by the offset circuit 155, showing waveforms obtained at each process step. A triangular waveform A is input, and is shifted upward in a predetermined range by operating the multipliers 153, 159 and the adder 169. The waveform A thus overflows in a dynamic range L, obtaining a waveform B. The waveform B is then shifted downward in a predetermined range employing the multipliers 161, 163 and the adder 171, resulting in a waveform C. Finally, the waveform C is shifted upward in a predetermined range by the multipliers 165, 167 and the adder 173. The resulting final waveform is shown as a waveform D. The process for obtaining the waveform D from the waveform A is defined as the offset process hereinafter.
The prior art sound processing system, however, can perform only limited patterns of the offset process for an input sound waveform since the combination of the multiplication coefficients of the multipliers is limited. Thus, in the conventional system the final waveform is produced by only a limited process, such as simple linear signal processing.